Chapter 6 Retrofit

Should You Retrofit or Rebuild? It is usually true that if you have og construction makes good a that isn't rotting into the Leconomic sense in areas where ground, it is probably worth retro- there are local trees to cut and use. fitting. This is especially true in So does making the effort to rescue remote communities of Alaska and rehabilitate our existing log where shipping costs and heating structures since the cost to erect fuel prices are very high. them has already been spent. Log building restoration We call this cost “embodied projects may also be for historical or energy.” Embodied energy is all the aesthetic reasons and not just for manufacturing, shipping, and labor energy efficiency. Very old buildings to build our homes the first time. may need many improvements to extend their life to reach their What is Payback? predicted payback time. Payback is all the money, work, and fuel that you save if you retrofit your house to become energy efficient.

Retrofit Checklist

The following checklist is meant to guide you through the assessment process and to focus your efforts on areas needing improvement. Details on how to do some of the work follow. Foundation and Floor Assessment

❏ Is foundation above the flood plain? Raise foundation elevation above high water mark.

❏ Is the floor level? Jack and level on existing foundation.

❏ Are foundation supports in good condition? Repair or replace pads/joists/ as necessary.

❏ Is foundation protected from moisture or wet soils? Raise floor joists at least 8 inches above ground—12 inches is even better. Install a capillary break between floor and foundation.

❏ Is the floor airtight without cracks and holes through the floor? Observe insulation installation at perimeter of floor below exterior and ensure the cavities are tight and full to minimize edge air intrusion. Air-seal at all floor penetrations, cracks, and perimeter

67 rim joists. Where space does not allow for working from below, airtight insulated skirting may be applied to the exterior of the rim joist area. Keeping the floor perimeter air tight is the key to comfortable and efficient floors. Do not interfere with the free flow of air under the house if it is built on permafrost.

❏ Does the floor insulation level meet the BEES R-value for the region (see Appendix A)? Add fiberglass or cellulose insulation between floor joists if space allows. Add rigid insulation to top of old floor with new plywood above where space does not allow placing fiberglass or cellulose in joist cavities.

❏ Is the insulation between the floor joists protected from critters? Sheath the bottom of the floor joists with plywood to support and protect insulation.

Log Assessment

❏ Does air leak in between the sill log and the floor? Caulk and seal the perimeter sill log to the floor membrane inside the house.

❏ Does the floor protrude beyond the sill logs outside of the building? If so, this shelf area can allow moisture from rain and snow to enter the structure. Use a wedge of cut from 2-by-4 or 4x4 to fill this area and caulk the top and bottom to the sill log and floor or use metal flashing to protect the shelf from weather.

❏ Are the logs of sufficient size to provide adequate insulation for the region? Select a design for increasing wall R-value. Apply wall insulation and furring to the interior or exterior.

❏ Are joints between the logs tightly sealed and chinked against air leakage? Apply appropriate Weatherall/Perma-Chink type material to joints.

❏ Are the logs in good shape around window and door penetrations? Test logs with a probe to determine their condition. Replace or treat wood at penetrations to prevent further deterioration.

❏ Does air leak around windows and doors? Remove trim and inspect the gap between the rough opening and frame. Remove fiberglass chinking and install backer rod and fill cavity with minimally expanding foam if settling is over (older buildings). Air seal the perimeter of windows and doors between the frame and the rough opening.

❏ Are log wall corner joints tight and sealed against air leakage? Test log ends with probe and treat to prevent further deterioration. Air seal as necessary with caulks or chinking.

❏ Are the upper gable end wall purlin and ridge penetrations sound and air tight? Use a probe to ensure wood condition is adequate

68 for supporting the roof. Apply air sealing measures to penetrations and purlin and ridge pole ends. Treat logs in these areas as needed to prevent further wood deterioration.

Roof and Ceiling Assessment

❏ Does the roof overhang protect the log walls from rain? Extend the overhang at eaves to move drip line away from walls and corners. Install gutters and direct runoff away from the foundation area. ❏ Does the top log to ceiling/roof joint show signs of leaking or staining? Apply air sealing measures to eliminate leakage. Add insulation as needed to improve thermal properties at this connection. Use a probe to ensure wood condition is adequate for supporting the roof. ❏ Does the roof show signs of water staining or dry rot? Inspect and probe the wood around chimneys and light (electrical) penetrations. Inspect areas around interior wall connections with ceilings. If the house has a cold roof, turn over insulation batts to locate air leaking from below. These leaks will show as dark and dirty areas in fiberglass batts. Seal air leaks from the attic side using acoustical sealant and poly patches. Seal air leaks in hot roofs from the interior using appropriate sealants if no major exterior roof replacement is planned. Treat chimney penetrations with utmost care and concern for fire potential. Replace or reinforce all roof supports that show signs of rot or deterioration. Add insulation to cold roofs only after all other work has been completed. Maintaining an airtight roof and ceiling is critical to the success of any project. ❏ Does the roof exterior show signs of potential leak areas or weather damage? Replace or repair shingles and metal as needed to prevent water entry. Replace or repair the flashing around penetrations in roofing. Install eave flashing to “kick” water away from facia boards. ❏ Does the roof cover all log ends? Cut off all log ends that extend beyond the drip line of the roof. ❏ Finish interior and exterior of logs as recommended in Chapter 7. ❏ Remember, use all resources available to you to make your decisions regarding log retrofits. The AHFC Resource and Information Center has a library of information available at no charge (1-800-478-4636). The University of Alaska Cooperative Extension has an energy and building specialist on staff to answer your questions (474-7201 or 1-800-478-8324). These and other resources are listed at the end of Appendix D.

69 So What Shape is Our House In?

Lower Log Condition

Check all lower logs for dry rot. The lower logs of buildings in ground contact will often be rotten beyond use and must be replaced. This can be a daunting task that requires digging, jacking, and sometimes rebuilding the floor-to-wall connec- tion as the bottom few logs are replaced. photo by Phil Loudon A new roof in Arctic Village. This may seem difficult, but it can help extend the life of a poorly insulated, energy-wasteful building 40 or 50 more years and save energy too. Where material and fuel trans- portation costs are high, this diffi- cult job will still pay back good savings.

Looking for Rot Around Log Penetrations

Where air leaks occur in buildings, moisture will build up and cause rot. Inspect all mechanical and rough opening penetrations before making any decision to retrofit an existing log house. Use an awl, ice- pick, or a sharp knife point to probe the wood around any opening in the log walls. Where the wood is rotten the probe will go in easily. photo by Phil Loudon The lower logs of buildings in ground contact will often be rotten Areas of good wood will resist your beyond use and must be replaced. efforts. Usually, the lower openings will contain rot from outside moisture while the upper penetrations will rot from exposure to inside mois- ture. Because windows may let snow, rain, or ice collect on the exterior sills, be sure to probe the exterior logs in these areas.

70 If wood around a window opening is rotten, there are two common ways to fix it: Option one is to make the rough opening bigger if it is possible to cut out the rot and make a surface for reinstall- ing the window, and add foam insulation to fill in the gap. Option two is to remove and replace the logs in the area of the opening. This is more expensive and so takes a longer time to pay back. If two or more windows have severe rot and logs need to be removed, go back and look at the project budget very closely. The This cabin was almost destroyed by rot. building may not be worth retrofit- ting.

Top Log Condition

The top log (cap log or plate log) is an area where air leaks open up over the years and moisture from indoors starts wood rot. When the temperature on the interior surface of the log drops, moisture will collect and possibly freeze on very cold days. This wetting, freezing, and drying cycle promotes rot. Use the same probing method to find rot in the logs and . You should also check the joint between the ceiling and the wall for The cabin was saved by cutting out all four log corners and air tightness and insulation. installing large vertical log corner posts. A good solution to use as much of the old building as possible. Note the trimmed roof logs and shorter porch.

71 One way to fix the top wall log has a high compressive strength to ceiling joint is by spraying that makes it suitable for such several inches of a two-part ure- installations. The covering plywood 3 thane foam into the wedge formed may be /4" tongue and . Use by the wall and ceiling (see illustra- a structural adhesive and apply it to tion, page 81). Then add a vapor all plywood edges, including the barrier (usually polyethylene , to construct an sealed with an acoustical sealant), airtight floor membrane. Seal the and finally cover it with a nice trim joint between the perimeter ply- board. wood and the log wall with a durable polyurethane caulk. Dry- 1 Let’s Start at the Bottom wall-type 3 /2-inch screws are used to fasten the plywood through the If you have enough room, a popu- foam, resulting in an additional lar way to add insulation to the R-10 insulation, an airtight floor, floor is to cover the existing floor and a new durable surface for the with rigid foam, and cover this finished flooring. with plywood. The negative associated with In many projects we have used this approach is that rigid foam two-inch extruded foam (usually insulation is a higher cost per blue, pink, or green) for the insula- R-value insulation than “soft” tion overlay. This rigid insulation insulations (fiberglass) and the

Some Problems to Look For

no insulation at rim joist

air gap above rotten or collapsed critters have easy access to insulation framing, causing floor damage insulation to sag

This floor is accessible and has floor joists that are deep enough for the minimum amount of insulation (see Chapter 3).

72 Observations from Arctic Village Sometimes, people cut logs in the spring and summer and then build with them in the fall. The logs may be only partially peeled or not peeled at all in some cases. When they build a house with logs like this, large cracks will develop in the logs after one year. First as the house is heated through the winter , the cracks will appear on the inside, and then the following summer as the sun heats the exterior, the cracks will appear on the outside. Eventually cold air will be able to travel completely through the cracks into the house, making the strucure very leaky . Another problem that results is that the cracks and unpeeled areas will catch rain and snow, which will eventually rot the logs. This will speed up the process of failure of the bottom logs that are providing the foundation, which in turn will help to destroy the rest of the building. Homes that are built in this manner are falling apart much faster than they should.

(comments from local resident, collected by Mimi Burbage)

new flashing

bottom log sealed against air leaks with caulk new rigid foam around the outside of the foundation

new fiberglass insulation installed tightly new two-part up against the foam sprayed floor, with no air on the rim joist pockets new sheathing to keep out animals

A large part of the decision to fix the old floor and reinsulate or build up the floor from the inside of the house depends on whether you can even get under the house. It is usually more labor to go under the house and fix the old insulation, but the materials can be cheaper.

73 plywood sealed to bottom log tongue and groove plywood caulked at rigid foam insulation fitted all joints. tightly between new 2-by cut to make a level floor

gaps in a severely warped floor filled with soft insulation

In spite of the insulation cost, it is less labor to install the insulation above the floor than work- ing below the floor, framing additional cavities and making other labor-intensive modifications.

Seal the joint between the perimeter plywood and the log and between sheets of plywood.

rigid foam insulation

glue designed for Don't line up plywood use with foam joints with foam joints.

Here is an example of adding rigid foam to the top of the floor without any additional framing. Be sure to stagger the joints of the foam so they don’t line up with the joints in the plywood.

74 3 added floor thickness of 2 /4 inches outside of the logs. This leaves the makes adjustments to doorways massive logs on the inside of the necessary. However, in spite of the thermal envelope and provides very insulation cost, it is less labor to effective thermal storage. Once the install the insulation above the logs are heated to room tempera- floor than working below the floor, ture, it may take days without heat framing additional cavities and for the logs inside the thermal making other labor-intensive envelope to cool off, even in an modifications. Alaskan winter. An exterior retrofit of a log Exterior Wall Retrofit house typically involves chain sawing off the log extensions at all The most energy-efficient way to corners of the building. Do not retrofit a log home is to attach an compromise the structural integrity insulated curtain wall on the

insulation

add a Tyvek or other brand air/weather barrier between the insulation and the 6-mil poly vapor barrier

siding

A three-sided log wall retrofitted with a stand-off wall, a good continuous vapor retarder, insulation, and siding. You can also use a 2-by-4 wall with 6 inches of insulation packed to fill in between uneven logs.

75 of the house by cutting off too off stud with a system of blocking much. The objective should be to and plywood gussets attached to remove any corner log ends that the logs on two-foot centers. First stick out beyond the curtain wall to establish the corner stand-off studs be attached. Remove any other plumb and at a distance from the projections that would interfere log wall to accommodate the de- with wrapping the exterior of the sired thickness of insulation. Use a log walls with a continuous 6-mil string line pulled tight between the poly vapor retarder. Pay particular corner studs to establish the align- attention to sealing the vapor ment of all the rest of the studs. retarder at the top and bottom and Sometimes the roof rafters can at all window, door, and utility support a hanging curtain wall. If penetrations. the house has not completely settled Since log walls are irregular, it (8 to 10 years in a dry climate), then will be necessary to fit each stand- be aware that the roof is still on its

Exterior Wall Retrofit vapor retarder

slot to allow for settling insulation

Tyvek or other brand house wrap

two options for stand- off wall attachment

6-mil siding poly vapor barrier

cover bottom to keep critters out

76 way down and attach the studs and Interior retrofit on a log wall the bottom plate in a manner that 2-by-4 stud 6-inch will allow for settlement. fiberglass It may be a good idea to wrap insulation attach to log wall with the insulated stand-off walls with a slots to allow settling weather retarder house wrap such as Tyvek or Barricade before install- ing horizontal beveled or rough-cut siding. The bottom of the wall should be covered with flash- vapor Sheetrock ing, plywood, or dimensioned retarder lumber to keep little creatures out.

l ica Interior Wall Retrofit ctr ele ns t tio igh ra As stated in the introduction, an irt et a en interior retrofit of a log home turns p the logs into very heavy and expen- sive siding, with all the thermal mass on the outside of the thermal envelope. Nevertheless, it is very Caulk vapor retarder common to fur in, run electrical to subflooring wiring, and insulate and vapor barrier walls constructed of small- diameter logs. This does indeed improve the thermal performance Attaching an interior wall to a three- of the wall, not only by increasing sided log exterior wall with a 2-by-6 the R-value but also by reducing the air leakage. The interior retrofit also reduces space and can make a small cabin 2-by-6 stud into a really small cabin. A simple way to add R-value to the inside without a lot of fastening problems is to use 2-by-4 studs and plates on the inside of the exterior walls. These should be installed tight to the logs and plumbed. Some shimming or shaving may be washer necessary to achieve a fairly straight wall, but this will depend on the quality of the original con- slots struction. vapor After the wall is fastened in retarder place, use 6-inch fiberglass insula-

caulk vapor retarder to subflooring

77 tion and pack it into the stud cavi- ties so that it fills the cracks be- tween the logs and provides a good friction fit. Even though the insula- tion is compressed in some areas, it old will still provide good insulating insulation Remove the old roof down to qualities since it will fill the voids the ceiling boards. If the ceiling adequately. is still in good shape it can be used again without removing. Install airtight electrical and This allows the building to be mechanical outlets before installing occupied while the roof is being the air-vapor barrier. replaced. Roof Retrofit new vapor retarder If the finished ceiling is still in good shape but the roof is under-insu- off the remaining overhanging ceiling lated or needs a vapor retarder, you boards. may consider cutting off the eaves with a chain saw at the outside of Wrap the house with a continuous vapor retarder the logs and running the new (6-mil poly or better). Care exterior wall vapor barrier of and craftsmanship are 6-mil poly up the wall and over the stressed at this point to get old roof and down the other wall. a good sealing balloon The gable-end wall vapor retarder effect to keep in warm air. should be caulked at the joint air space between the log and the ceiling as well as where the log meets the floor at the bottom of the wall. Lap over and seal the vapor retarder to the other sheets of poly at the four corners. Place this exterior 6-mil polyeth- ylene wrap on the warm side of the Add an exterior wall with a thermal envelope. Whether in the vapor retarder and insula- wall or roof system, at least two 1 2 tion. Observe the /3– /3 rule thirds of the R-value must be on the (see opposite page). cold side of the vapor retarder to keep the humidity in the air warm enough so it doesn’t condense into liquid water inside the wall or roof. Build up a new roof on top of the vapor old, taking care to protect the vapor retarder retarder during construction.

78 Hot Roof Retrofit If you put a new air barrier on top of the existing roof, and more “At least two insulation and roofing above it, Hot roofs are typical in log build- thirds or more of ings with traditional purlin and then the building science one- ridge pole exposed ceilings. Here thirds/two-thirds rule must be the R-value must the insulation is installed between rigidly adhered to. This rule helps be on the cold the roof rafters. By definition, the you locate the air/vapor retarder in side of the vapor hot roof does not provide ventila- instances where the barrier might tion. It usually has no access for be placed between two insulation retarder. In the installing additional insulation. layers. If there is an air gap over the far north, at least Ventilated hot roofs are being old insulation, pack the area above three quarters the outside walls to maintain a constructed on newer log build- should be on the ings, however, this is a recent continuous blanket of insulation on development and it is rare to find all six sides of the house: four walls, cold side. such designs in older log cabins floor, and roof. and houses. You must first determine which ” surface to add the insulation to, inside or outside. If the roof con- sists of leaky shingles and rotten plywood, the obvious area to modify would be the outside. Strip off the shingles, install a vapor retarder, put insulation on the outside of the vapor retarder, and reinstall roofing. The inside is a better approach because it is easier to get an airtight installation. Framing additional ceiling surface supports and insu- lating between the top log and purlin and between the purlin and

ridge pole have proven successful, photo by Phil Loudon although this covers most of the log An interior retrofit of a ceiling in progress; note new electrical ceiling and may not appeal to some wires being installed. owners. It is most important to locate the surface that will serve as the air barrier or vapor retarder if you put more insulation on the outside of a hot roof. If it will be the interior surface, great care must be taken to make it truly airtight, because if air leaks into the roof, the moisture carried in the air will damage the roof.

79 Cold Roof Retrofit “Water vapor in What’s a Dewpoint ? the air gets The dewpoint is the temperature at We typically call a truss roof a cold cooler as it which moisture condenses from vapor roof because the space above the into water. Water vapor in the air in insulation is ventilated to the moves out the house gets cooler as it moves out outside. While not always venti- through the wall and roof, and at through the wall some point it condenses. If this temp- lated, this attic space is designed to and roof. If it erature is inside the wall of the house, be significantly colder than a hot condenses inside it will cause rot. This is why at least roof, where ventilation space is two-thirds of the R-value of your minimal or nonexistent. The cold the wall of the insulation must be outside of the roof can receive more insulation vapor retarder. In the far north at house, it will least three quarters should be on the since space is usually available. cause rot. cold side. Before putting more insulation dew point in the attic, seal all ceiling and attic penetrations to prevent any air temperature ” leakage from carrying moisture into vapor retarder the attic space. This is usually done from the attic (top) side by finding each leak and applying a heavy of acoustical sealant around the penetration and embedding a patch of polyethylene into the sealant. Tape this patch in place so it won’t move around. Do this to all vapor retarder penetrations and breaks in the air/ vapor barrier, including partition walls. This is not the place to skimp or save on acoustical sealant. vapor retarder stops After all air sealing has been moisture-laden air from done, you should measure the entering wall space distance between the outside edge of the wall and the underside of the roof plywood or metal. If room dew point exists for meeting the minimum temperature recommended BEES insulation, then proceed with putting new insulation in place. However, most older roofs don’t have enough space to allow for high levels of insulation over the wall. Use a rigid insulation that has a high R-value per inch such as foamboard where space is tight. Cutting the rigid material to

moisture-laden air condenses inside wall, causing damage

80 fit tightly into the cavity is impor- tion temperature occurs. It will tant! By placing three layers of two- ignite and burn easily at much inch polyisocyanurate rigid foam lower temperatures. insulation (R-48), you can come Maintaining a good air gap closer to meeting the minimum around the insulated pipe above the recommended BEES standards than ceiling is also necessary, and more is would be possible using soft insula- better here. If the attic contains lots tions (fiberglass) in this tight space of insulation, you should extend the over the wall. insulation dam (a sheet-metal cylinder around the chimney) to Chimney and Flue prevent insulation from getting into Penetrations the air gap surrounding the chim- ney. The dam should always be left This is an area of frequent failure in open at the top to allow air currents all types of roofing. There are two to cool the space between the dam potential problems: chimneys and chimney. Always follow the located too close to wood are a fire manufacturer’s instructions. Just hazard, and leaks can develop in following codes and regulations the roof around chimney penetra- may not be enough to prevent the tions, leading to rot. wood framing from turning into Research has shown that where fuel. heating appliances are near wood, a Chimneys typically found in significant drop in the wood igni- older buildings must be improved

air space above sub-standard truss fiberglass insulation rigid foam 2x4 nailer

vapor retarder ceiling boards vapor trim board retarder vapor retarder batt or plate log blown-in two-part foam insulation

stack rigid insulation

rigid foam in truss-style roof with attic

One way to fix the joint between the top wall log and the ceiling is by spraying several inches of a two-part urethane foam into the wedge formed by the wall and ceiling. Then add a vapor barrier (usually polyethylene sealed with an acoustical sealant), and finally cover it with a nice trim board.

81 to prevent moisture from entering Note that different caulks and framing members in the roof and sealants are used to provide for a ceiling. Therefore, care must be complete and airtight seal around taken to eliminate all air leakage the chimney and to the surrounding around chimneys. See the illustra- drywall. Use a high-temperature tions for examples of how to do this heat rated RTV silicone caulk for safely. air-sealing the trim ring to the insulated chimney.

This stove pipe and chimney are This is an example of a proper installa- overdue for a good safety upgrade tion of a chimney and stove pipe. and retrofit.

metal insulated at least metal insulated at least chimney 2" air space chimney 2" air space

attic attic extension extension to metal to metal insulation 18" insulation dam dam 18"

acoustic sealant

vapor retarder

Sheetrock acoustic sealant Sheetrock trim collar trim collar metal insulated high-temperature metal insulated chimney RTV silicone chimney sheet metal slip joint per flashing manufacturer’s recommendation single-wall pipe to single-wall pipe to high-temperature heater (typical) heater (typical) RTV silicone

Attic side air seal (typical on new construction) Interior side air seal (typical on retrofit)

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